Title from PDF of title page. / Document formatted into pages; contains 86 pages. / Thesis (M.S.Ch.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The goal of this thesis is to present the design and development of a chemical vapor deposition reactor for the growth of high quality homoepitaxy silicon carbide films for electronic device applications. The work was performed in the Nanomaterials and Nanomanufacturing Research Center at the University of South Florida from 8/2001-5/2003. Chemical vapor deposition (CVD) is the technique of choice for SiC epitaxial growth. Epitaxial layers are the building blocks for use in various semiconductor device applications. This thesis reports on a SiC epitaxy process where a carrier gas (hydrogen) is saturated with reactive precursors (silane and propane) which are then delivered to a semiconductor substrate resting on a RF induction heated SiC coated graphite susceptor. Growth proceeds via a series of heterogeneous chemical reactions with several steps, including precursor adsorption, surface diffusion and desorbtion of volatile by-products. / ABSTRACT: The design and development of a reactor to make this process controlled and repeatable can be accomplished using theoretical and empirical tools. Fluid flow modeling, reactor sizing, low-pressure pumping and control are engineering concepts that were explored. Work on the design and development of an atmospheric pressure cold-wall CVD (APCVD) reactor will be presented. A detailed discussion of modifications to this reactor to permit hot-wall, low-pressure CVD (LPCVD) operation will then be presented. The consequences of this process variable change will be discussed as well as the necessary design parameters. Computational fluid dynamic (CFD) calculations, which predict the flow patterns of gases in the reaction tube, will be presented. Feasible CVD reactor design that results in laminar fluid flow control is a function of the prior mentioned techniques and will be presented. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 107-110). Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 112-119). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 168-180).

Diamond and diamond-like carbon films, with their exceptionally good mechanical, chemical, and optical properties, are the best materials as protective hard coatings for electronic devices and cutting tools. The biocompatibility of these materials makes it suitable for bone implants. The wide range applications of these films are hindered because of the high compressive stresses developed during the deposition. Use of carbide and nitride interfacial layers has emerged as one of the methods to reduce the compressive stresses.The present research focuses on the study of different materials as the interfacial layers for diamond and tetrahedral amorphous carbon films. For tetrahedral amorphous carbon AlN, Ta, TiN, TiC, TaN and W were investigated as the interlayer materials. The interlayer was deposited at different substrate temperatures to study the temperature induced changes in the residual stress. The tetrahedral amorphous carbon with TiN interlayer deposited at 300°C and 600°C exhibited a maximum reduction in the stress.TiN and TiC were deposited as interlayer for the diamond films on Ti-6Al-4V alloy. TiC has improved the adhesion of diamond with the substrate and exhibited less compressive stresses compared to TiN.

The heteroepitaxial growth of cubic silicon carbide (3C-SiC) on (111) silicon (Si) substrates, via a horizontal hot-wall chemical vapor deposition (CVD) reactor, has been achieved. Growth was conducted using a two step process: first the Si substrate surface is converted to SiC via a carbonization process and second the growth of 3C-SiC is performed on the initial carbonized layer. During carbonization, the surface of the Si is converted to 3C-SiC, which helps to minimize the stress in the growing crystal. Propane (C3H8) and silane (SiH4), diluted in hydrogen (H2), were used as the carbon and silicon source, respectively. A deposition rate of approximately 10 µm/h was established during the initial process at a temperature of ~1380 °C. The optimized process produced films with X-ray rocking curve full-width at half-maximum (FWHM) values of 219 arcsec, which is significantly better than any other published results in the literature. Once this process was developed a lower temperature process was developed at a slower growth rate of ~2 µm/h at 1225 °C. The crystal quality was inferior at the reduced temperature but this new process allows for the growth of 3C-SiC(111) films on oxide release layers for MEMS applications. In addition, for electronic device applications, a lower temperature process reduces the generation of defects caused by the nearly 8 % mismatch in the coefficient of thermal expansion (CTE) between 3C-SiC and Si. Finally a new process using a poly-Si seed layer deposited on an oxide-coated Si wafer was used to form 3C-SiC films for MEMS applications. The results indicated initially that the films may even be monocrystalline (based on X-ray evaluation) but later analysis performed using TEM indicated they were highly-ordered polycrystalline films. The grown 3C-SiC films were analyzed using a variety of characterization techniques. The thickness of the films was assessed through Fourier Transform infrared (FTIR) spectroscopy, and confirmed (in the case of growth on poly-Si seed layers) by cross-section scanning electron microscopy (SEM). The SEM cross-sections were also used to investigate the 3C-SiC/oxide interface. The surface morphology of the films was inspected via Nomarsky interference optical microscopy, atomic force microscopy (AFM), and SEM. The crystalline quality of the films was determined through X-ray diffraction (XRD).

In this thesis, a systematic study has been carried out on the synthesis, characterization and applications of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) thin films deposited by the chemical vapor deposition (CVD) method. Firstly, an overview of diamond films synthesized from carbon-containing gas plasmas is presented. A parameter study was performed to grow diamond thin films. The transition from micro- to nanocrystallinity of diamond grains was achieved by controlling the Ar/Hydrogen gas ratio. The nanocrystallinity is the result of a new growth mechanism which involves the insertion of carbon dimmer into carbon-carbon and carbon-hydrogen bonds. Secondly, characterization of diamond films has been carried out by different techniques including electron microscopy, near edge X-ray absorption fine structure (NEXAFS), nanoindentation, and Raman spectroscopy. Unique properties of NCD, compared to those of MCD grown by conventional hydrogen rich plasma, have been observed and investigated. Thirdly, various applications of diamond films are discussed: a). Well-adhered MCD coatings have been deposited on WC-Co substrates with proper surface pretreatment. A diffusion barrier Cr/CrN/Cr was deposited on the cemented carbide substrate and the substrate was short peened with 150 micron friable diamond powders to achieve higher nucleation density and stronger adhesion strength; b). A nitrogen doped NCD based biosensor was fabricated for glucose sensing. Carboxyl functional group and conducting polymer (polyaniline) have been utilized respectively to electrochemically functionalize the diamond surface. A linear response to glucose concentration has been obtained from the electrode with good sensitivity and stability; c). A novel approach to synthesize NCD wires has been developed for the first time. The NCD coating was successfully coated on Si nanowires (SiNWs) to form NCD wire with diameter around a few microns. This study opens a whole new area for applications based on diamond wires such as neural transmission electrodes, field emission emitters, and electrochemical electrodes with improved properties

The heteroepitaxial growth of cubic silicon carbide (3C-SiC) on silicon (Si) substrates at high growth rates, via a horizontal hot-wall chemical vapor deposition (CVD) reactor, has been achieved. The final growth process was developed in three stages; an initial "baseline" development stage, an optimization stage, and a large area growth stage. In all cases the growth was conducted using a two step, carbonization plus growth, process. During carbonization, the surface of the Si is converted to 3C-SiC, which helps to minimize the stress in the growing crystal. Propane (C3H8) and silane (SiH4), diluted in hydrogen (H2), were used as the carbon and silicon source, respectively. A deposition rate of approximately 10 um/h was established during the baseline process. Once the baseline process proved to be repeatable, optimization of the process began. Through variations in temperature, pressure, and the Si/C ratio, thick 3C-SiC films (up to 22 um thick) and high deposition rates (up to 30 um/h) were obtained. The optimized process was then applied to growth on 50 mm diameter Si(100) wafers. The grown 3C-SiC films were analyzed using a variety of characterization techniques. The thickness of the films was assessed through Fourier Transform infrared (FTIR) spectroscopy, and confirmed by cross-section scanning electron microscopy (SEM). The SEM cross-sections were also used to investigate the 3C-SiC/Si interface. The surface morphology of the films was inspected via Nomarsky interference optical microscopy, atomic force microscopy (AFM), and SEM. The crystalline quality of the films was determined through X-ray diffraction (XRD) and low-temperature photoluminescence (LTPL) analysis. A mercury probe was used to make non-contact CV/IV measurements and determine the film doping.

This dissertation research focused on the growth of 4H-SiC epitaxial layers in low-pressure horizontal hot-wall chemical vapor deposition (CVD) reactors. The goal of the research was to develop a growth process that maximized the growth rate and produced films of smooth morphology. The epitaxial growth of SiC was carried out in two different reactor sizes, a 75 mm reactor and a 200 mm reactor. The maximum repeatable growth rate achieved was 30-32 um/h in the 200 mm reactor using the standard chemistry of hydrogen-propane-silane (H2-C3H8-SiH4) at growth temperatures <̲ 1600 °C, which is the highest growth rate reported to date in a horizontal hot-wall reactor at these temperatures. This growth rate was achieved with a silane flow rate of 30 sccm. The process development and characterization of 4H-SiC epitaxial films grown using the standard chemistry are presented. There are many ways to increase the growth rate, such as changing the pressure, increasing the reactant flow rates, or increasing the temperature. The method of choice for this dissertation work was to first increase the reactant flow rates, i.e. silane flow rate, and then to alter the growth chemistry by using a growth additive. When the silane flow is increased, while maintaining a specific growth temperature, supersaturation of silicon may occur. When this happens, particulates may form and deposit onto the sample surface during growth which degrades the film morphology of the epitaxial layers. In order to overcome this severe limitation in the growth of SiC, hydrogen chloride (HCl) was added to the standard chemistry of H2-C3H8-SiH4 during growth when the SiH4 flow was increased beyond 30 sccm. With the addition of HCl, the Si supersaturation was suppressed and the growth rate was increased from ~32 um/h to ~ 49 um/h by increasing the silane precursor up to 45 sccm, while maintaining the Si/C ratio of the standard chemistry process. The addition of HCl to the standard chemistry for growth of SiC films was pioneering work that has since been duplicated by several research groups.

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